The following prior art publications are considered as being relevant for an understanding of the invention.
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DNA profiling has become a major tool in the forensic world [1]. The current gold standard for forensic DNA profiling is the sizing of 9-15 short tandem repeat (STR) markers [2]. This method has been found to be very efficient for analyzing DNA profiles from specimens containing DNA from a single individual or a simple mixture of two individuals. However, the identification of an individual in complex mixtures (usually more than two individuals), has proven to be difficult [3, 4].
A number of studies have proposed to use bi-allelic single nucleotide polymorphisms (SNPs) for forensic identification [5-7]. These studies propose using SNPs with allele frequencies close to 0.5 in order to increase statistical power. For a given individual, and it is determined to what extent the individual's DNA, if present in the mixture can account for any difference in allelic frequencies in the mixture and the population at large. In a recent study, the use of high density SNP microarrays (including 500,000 SNPs or more) was shown to enable the identification of an individual in complex mixtures [8]. That study noted that with the large amount of information on allele frequencies of hundreds of thousands of SNPs, one can identify the presence of a single individual when the genotype of the individual is known for the same hundreds of thousands of SNPs, even if the DNA mixture contains DNA from thousands of individuals. The study was mainly presented in the context of the anonymity of individuals participating in large genome-wide association studies (GWAS). The use of their method for forensic purposes is suboptimal for various reasons. First, the method does not efficiently allow the exclusion of relatives, giving the defense an opportunity to claim that the suspect's relative rather than the suspect himself is represented in the mixture. Second, the method requires accurate allele frequency data for an appropriate reference population, which in many instances might not be available. Third, genotyping hundreds of thousands of SNPs provides genetic information which might be sensitive with regards to protecting individuals' privacy. Lastly, genotyping hundreds of thousands of SNPs is costly for the routine use in forensic laboratories.